PVD on STM32L4 with external input

[CanRF]

Hi

On STM32L4xx Ref Man 

Programmable voltage detector (PVD) supports external input PVD_IN.

How to configure the GPIO for PVD_IN (ex STM32L4 PB7)?

How to configure VREFINT?

Is there any example?

[RomainR.]

Hello @CanRF 

As an example on STM32L476 device (Nucleo-L476RG)

According to DS10198 Rev 11 in Table 16. PVD_IN is an additional function connected to PB7. 
And in RM0351 Rev10, PVD can be configured in PWR_CR2 bits PLS[2:0] = 111.

In STM32CubeMX here the possible PVD levels configurations:

The internal voltage reference VREFINT is calibrated in production with VDDA=VREF=3.0V at 30°C, is around 1.2V (see DS10198 Table 26) and it is enabled when VDDA and VSSA are supplied.

Best regards,

Romain,

[CanRF]

Hi Romain

Thanks for your information.

DS10198 Rev 11 and RM0351 i read before. But I didn't see information for the GPIO configuration nor the VRefint configuration.

From MX Cube I see, that PB7 is configured as analog with no pullup/down.

This was also my intention but i didn't find it in the docs.

Where did you get the information, that VRefint is available when VDDA and VSSA are supplied?

For ADC conversion of VRefInt VREFEN of ADCx_CCR must be enabled.

Can PVD use VRefInt Independent of ADC and VREFEN?

Thanks for clarification

Best regards, 

RF

[RomainR.]

Hi @CanRF 

Sorry, I made a mistake and I misled you. I mixed up the VREFINT bandgap with the VREFBUF.

I'm referring to RM0351 in section 5 Power control (PWR)

• VREFINT is powered by VDD (not VDDA) and is related to Power management (PMU) 

• The VREFEN control bit is specific to ADC input for internal conversion.

When PLS[2:0] = 0b111 in PWR_CR2 register. The external input analog voltage PVD_IN is compared internally to VREFINT. It's independent from ADC.

Best regards,

Romain,

[CanRF]

Hi Romain

Again thanks for your information.

This helps a lot,

But now I've an additional problem.

On startup I want to wait until the power is over the selected voltage.

So I configure PVD and wait until PDVO is 0.

 I use the following code

...

    HAL_PWR_ConfigPVD(&sInit);

    LL_PWR_EnablePVD( );

    while(0U != LL_PWR_IsActiveFlag_PVDO( ))

    {

    }

...

But PVDO is always 0 after PVDE is set.

I think the PVD need some time to startup.

I test a delay between LL_PWR_EnablePVD( ); and LL_PWR_IsActiveFlag_PVDO( ).

With about 160us PVDO has the correct value.

Is this time and behavior anywhere documented.

Thanks for clarification.

RF